1. Field of the Invention
The present invention relates to a method of freezing, in particular to method of ensuring the use of brine with optimal composition for freezing various food products and biological samples.
2. Description of the Related Art
Methods of freezing food products for long duration preservation and freezing biological samples for cytological or histological examination are known and available. For example, liquid nitrogen is a conventional method for freezing food or biological samples. Nevertheless, this method is costly since the liquid nitrogen is expensive.
Using cooled brine (antifreeze solution) is another conventional freezing method. Brine includes inorganic substances such as calcium chloride, and organic substances such as ethylene glycol and propylene glycol. This method is advantageous, because it achieves greater cooling at a comparatively lower price.
For example, “A Method of Freezing Fishery Products” is known from U.S. Pat. No. 4,601,909 issued to Nagoshi on Jul. 22, 1986. This method includes the steps of preparing a brine containing rapeseed oil, propylene glycol, calcium chloride and water, cooling the brine and immersing the seafood in the cooled brine until it is frozen. This method reduces or eliminates breakdown of muscle tissue in the seafood. Hence, deterioration in quality of the frozen product is prevented or reduced.
A similar process for “Quick Freezing of Meat” is disclosed and claimed in U.S. Pat. No. 4,654,217 issued to Nagoshi on Mar. 31, 1987. The disclosed process is similar to that disclosed in U.S. Pat. No. 4,601,909 except that it is applicable to beef, poultry, pork and the like.
U.S. Pat. No. 4,657,768 issued to Nagoshi on Apr. 14, 1987, discloses a “Freezing Method for Perishable Foods” which includes placing a perishable food in a heat conducting container and causing the other surface of the heat conducting container to contact cooled brine or a liquefied gas. Accordingly, the perishable food is frozen quickly without immersion.
U.S. Pat. No. 4,689,963 issued to Sakai on Sep. 1, 1987, relates to a method of freezing foods. The method of Sakai is similar to the methods of Nagoshi except that a layer of brine is placed in the heat conducting container along with the perishable food. Freezing proceeds only from the portion which is in contact with the brine and the potential for the food to stick to the container is reduced.
U.S. Pat. No. 7,022,360 issued to Liberman et al. provides an improved method of marinating and reconstituting meat from trims of fish, poultry, pork, beef or the like. The method comprises the steps of freezing the trims, adding marinade to the frozen trims and compressing the frozen trims to a sufficient pressure to lower the freezing point below the temperature of the frozen trims such that the marinade is diffused through the trims and purge is formed on the outer surface of the trims so as to hold the trims together.
U.S. Pat. No. 4,840,034 issued to Liberman provides a method of freezing vital body fluids for storage. The method includes the steps of preparing a brine including a cruciferous oil, cooling the brine, providing a heat transfer container having a vital body fluid therein and subjecting the heat transfer container to a heat transfer relationship with the cooled brine for a period of time sufficient to freeze the vital body fluid in the heat transfer container.
U.S. Pat. No. 4,840,035 issued to Liberman et al. provides a method of freezing a tissue specimen by using a brine comprising a cruciferous oil.
U.S. Pat. No. 5,001,047 issued to Liberman provides a method of preserving harvested viable organs for transplant. The method includes the steps of preparing a brine including a cruciferous oil and a glycol, cooling the brine, and subjecting the harvested viable organ to the cooled brine in order to chill the viable organ and maintain its viability.
All of the above cited references are herein incorporated by reference in their entireties.
According to the above cited references, maintaining the composition of a brine in a desired balance, i.e., with each ingredient contained therein being in a predetermined proportion, is very important for attaining desirable results, e.g., minimization of weight loss and deterioration of the taste of a food product, reduction of damage to the muscular tissue of a meat product or a tissue sample, and maintenance of the viability of vital body fluids such as sperm, eggs, zygotes, blood and the like over an extended period of time.
As a brine, in which each component is in a predetermined proportion, is used over time the brine becomes gradually “out of balance”, i.e., at least one component may not be in the predetermined proportion, due to, e.g., different rates of evaporation. Many brine formulations are naturally hydroscopic and when they absorb moisture from the surrounding atmosphere go “out of balance.” In other words, the proportion and amount of brine ingredients with respect to each other will no longer be at optimal levels. There is also the possibility that the brine may be gradually contaminated. The total amount of brine may also be reduced to a sub-optimal amount after being used over time. As a general practice, brine suppliers often specify or recommend that brine, after being used for a certain period of time, should be replaced with a certified balanced new brine. Because the brine typically gradually degrades, the physical change of the brine based on the brine's appearance is not dynamic. Thus, users tend to ignore the supplier's recommendation to replace the brine and continue using the brine after it expires. The quality of the frozen product or sample so frozen, freezing efficiency, and/or operating cost is, therefore, significantly compromised.
Therefore, there is a need for a method of ensuring that a brine for freezing is used in an optimal composition, and the brine, upon being “out of balance”, is timely replaced, in particular for the application of brine in food or medical industry.